Answer:
M = 1170 g
Step-by-step explanation:
Mass = density × volume
M = p x v
M = 78 x 15
M = 1170 g
But i really need a name of this book and authors :)
Next time make it more easyer
Answer:
4800
Step-by-step explanation:
length = 20mm X 3 = 60mm
width = 20mm X 4 = 80mm
area = length X width = 60 X 80 = 4800 m
I hope it helps you!